3 mm EPR investigation of the primary donor cation radical in single crystals of Rhodobacter sphaeroides R-26 reaction centers

Burghaus, Olaf; Plato, M.; Bumann, Dirk; Neumann, Britta; Lubitz, Wolfgang; Möbius, K.

doi:10.1016/s0009-2614(91)85079-c

Cited by 27 publications

(14 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This crosscheck reveals no effect on the spectra, which in turn suggests that the linewidth is not affected by exchangeable protons. These values are in reasonable accord with Burghaus et al [21], who obtained and analyzed W-band spectra of protonated P~-65 reaction centers from R-26. P+65 is thought to be a pair of bacteriochlorophylls (dimeric cation radical form), presumable resembling a delocalized ~-radical.…”

Section: Vhf Epr As An Integral Part Of a Multifrequency Strategy: Ahsupporting

confidence: 91%

Very high frequency EPR — 94 GHz instrument and applications to primary reaction centers from photosynthetic red bacteria and to other disordered systems

et al. 1994

View full text Add to dashboard Cite

Abstract. There are many advantages to carrying out electron paramagnetic resonance experiments at very high frequencies, either as part of a multifrequency strategy for solving problems of for special characteristics of high frequencies. These special characteristics include the potential for high point sensitivity, enhanced resolution, separation of similar species, altered sensitivity to motion, suppression of motional effects, and many others. This paper describes a three-millimeter-wavelength (W-band, 94 GHz) EPR spectrometer built for a multi-user facility and illustrates with some examples, most of them being disordered systems. One significant example is the oxidized primary reaction center, P+~5, isolated from the red photosynthetic bacteria Rhodobacter Sphaeroides R-26. The W-band technique applied to both centers isolated from bacteria grown from either deuterated or ordinary growth media allows extraction of the full g anisotropy in these centers and sets the stage for multifrequency EPR spectroscopy to yield a full analysis of the various contributions to linewidths in these systems.

show abstract

Section: Vhf Epr As An Integral Part Of a Multifrequency Strategy: Ahsupporting

confidence: 91%

Very high frequency EPR — 94 GHz instrument and applications to primary reaction centers from photosynthetic red bacteria and to other disordered systems

et al. 1994

View full text Add to dashboard Cite

show abstract

“…The principal values of the g-tensor of the primary donor cation of deuterated and protonated RC of Rb. sphaeroides R26 have been reported by three independent groups using W-and D-band continuous wave (cw) EPR (96)(97)(98) (99) were taken along the crystal axes and do not represent the main g-tensor components. It should be noted that the Novosibirsk group's g-tensor values differ significantly from those cited above.…”

Section: Chlorin and Bchl Radicalsmentioning

confidence: 99%

“…sphaeroides R26 was achieved (96,99). Due to the size and symmetry of the unit cell, containing four magnetically inequivalent RC, an ambiguity of four possible orientations of the g-tensor with respect to the molecular frame existed.…”

Section: Chlorin and Bchl Radicalsmentioning

confidence: 99%

Radicals and Radical Pairs in Photosynthesis

Angerhofer

Bittl

1996

Photochem & Photobiology

View full text Add to dashboard Cite

“…This field strength is a factor of -30 greater than that used for conventional EPR spectroscopy. Other high-field studies have been carried out on various biological radicals (14)(15)(16)(17). The tyrosyl radical has been studied in PSII by Gulin et al (16) at 135 GHz and in ribonucleotide reductase by Gerfen et al (15) at 140 GHz.…”

mentioning

confidence: 99%

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance.

Brunel

Brill

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The 4 K 245-GHz/8.7-T electron paramagnetic resonance spectrum of the stable tyrosyl radical in photosystem I, known as TyrD, has been measured. Illumination at 200 K enhances the signal Intensity of TyrD" by a factor of >40 compared to the signal obtained from darkadapted samples. This signal ehncement and the unusual ine shape of the TyrD' resonance result from the magnetic dipolar coupling of the radical to the manganese duster involved in oxygen evolution. The relative alar orientation of the m _ cluster with respect to TyrD-has been determined from line-shape analysis. The resonance arising from TyrD' in Tris-washed nsfree photosystem U sample is also distorted. This effect probably originates from the influence of the nonheme iron on the spin aon of the tyrosyl radical.The relative angular orientation of the nonheme iron has also been determined. Oriented samples were used to determine the angular orientation of TyrD with respect to the membrane plane. Combining angular data with pubilshed distances, we have constructed a three-dimensional picture of the relative positions of TyrD', the manganese cluster, and the noneme iron. The data suggest a more symmetrical placement of the manganese relative to TyrD-and TyrZ, the tyrosine involved in eleco transfer, than is usually assumed in current models of photosystem H.At low temperatures, the electron paramagnetic resonance (EPR) signal of the stable tyrosyl radical, known as TyrD- (1, 2), from plant photosystem II (PSIT) is known to be "relaxation enhanced" when the sample is illuminated at 200 K (3, 4). This enhancement has been attributed to the presence of a second paramagnetic species that is capable of increasing the relaxation rates of the tyrosyl radical through a dipolar interaction. The second paramagnet is thought to be the manganese cluster that is involved in charge storage and probably acts as the active site for oxygen evolution (5, 6). The dipolar spin-relaxation mechanism has been thoroughly studied (7-9). The strength of the dipolar interaction is determined by the distance between the two spins and the angle between the interspin vector and the applied magnetic field. Previous work on PSII has concentrated on the determination of the interspin distance (10-13). No attempts have been made to obtain the angular orientation of the two spins.At magnetic field strengths used in conventional EPR spectroscopy, the spectrum of the tyrosyl radical is dominated by the hyperfine interactions between the electron spin and its neighboring protons. The inhomogeneous line width of the spectrum is determined by the anisotropic parts of these hyperfine interactions and the g anisotropy, each of which has its own particular orientation dependence relative to the molecular frame. A good approximation is that all possible orientations ofthe radical with respect to the applied magnetic field contribute to a given field position on the TyrD spectrum. Thus, the determination ofthe orientation of an external relaxer is difficult. However, at magnetic fields m...

show abstract

3 mm EPR investigation of the primary donor cation radical in single crystals of Rhodobacter sphaeroides R-26 reaction centers

Cited by 27 publications

References 12 publications

Very high frequency EPR — 94 GHz instrument and applications to primary reaction centers from photosynthetic red bacteria and to other disordered systems

Very high frequency EPR — 94 GHz instrument and applications to primary reaction centers from photosynthetic red bacteria and to other disordered systems

Radicals and Radical Pairs in Photosynthesis

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance.

Contact Info

Product

Resources

About